The Study Of 1-MCP Physiological Regulation On Rubbery Papaya Fruit And The Related Genes Expression

Papaya?Carica papaya L.?is a climacteric fruit,it develops physiological disease during postharvest storage which resulted a significant impact on long term storage and transportation.1-MCP treatment can effectively repress ethylene signal transduction,extend shelf life and retain freshness.But a certain concentration of 1-MCP treatment can induced 'rubbery texture' of 'Risheng' papaya fruit,with deterioration of fruit qualities.The present study will focus on 'Risheng,papaya fruit which responses to different concentration of 1-MCP.The effects of' exogenous ethylene on papaya fruit 'rubbery texture'.The effects of 1-MCP on expression of papaya fruit softening related genes..The results were summarized as follows:?1?The effects of 1-MCP treatment with different concentrations?0,0.05,0.1,0.2,0.3,0.4,0.5 and 1 ?L L-1?on papaya fruit ripening were studied in this paper.The results indicated that:1-MCP treatment with different concentration could inhibit the decrease of fruit hardness,At 18 day,the hardness of different 1-MCP treatment fruits ware higher by 0.468?0.508?0.492?0.536?0.542?0.551?0.579 kg·cm-2 than control respectively.1-MCP had a significant effect on cell wall degrading enzymes,at 24 day,fruit hardness of different 1-MCP treatment were lower by 1.026?25.954?10.776?27.084 ?g ·ml-1 min-1 than CK respectively?p<0.01?.It was found that treatment of 1-MCP?0.05,0.1,0.2 ?L·L-1?just delay the drop of hardness;but the concentration of 0.3,0.4,and 0.5 and 1 ?L·L-1 caused papaya fruits happen 'rubbery'.Therefore,0.3 ?L·L-1 were the threshold concentration that 1-MCP caused papaya fruits 'rubbery '.?2?Effects of ethephon?0.5 g·L-1?treatment on storage quality and softening of papaya fruits which were pre-treated by 1-methylcyclopropene?1-MCP?for 10,20,and 30 days were studied.The results indicated that:the treatment of ethephon can promoted the drop of fruit hardness,the decline range of 1-MCP+?10 d?ETH,1-MCP +?20d?ETH,1-MCP +?30d?ETH were 3.976%,5.272%and 4.972%respectively,and the water soluble pectin content increased by 0.489%,0.621%and 0.328%respectively during storage period,the active value of endo-1,4-Xyl were 63.359,75.118,69.578 ?·ml-1·min-1 at 6 d.Therefore,after the treat of ethephon,rubber-papaya softening,water-soluble pectin content increased,the activity of cell wall degrading enzymes be enhanced.?3?To better understand the role of 1-MCP on papaya fruit 'rubber texture',the expression and RPKM of endo-1,4-Xyl genes?evm,TU.supercontig₁06.45 and evm.TU.supercontig₁60.19?,endo-1,3-Glu gene?evm.TU.supercontig₂.231?,?-Gal gene?eevm.TU.superconlig₉3.34?were investigate based on real-time qPCR and transcriptomics Study.The results showed that:1-MCP treatment significantly inhibited expression and transcription of all genes that were mentioned above.At 9 days,RPKM value were 8.816,2.123,19.349,416.465 in 1-MCP treatment fruit respectively,significant lower than 48.595,5.429,50.131,923.543 in control fruits.At 6 days,relative expression of 1-MCP treatment fruits were 0.169,0.017,0.149,0.117 respectively,lower by 1.376,0.083,1.02,0.224 than control.The results suggested that the low expression and transcription of these genes play an important role in papaya fruit 'rubber texture'.In one word,treatment of 1-MCP?0.05,0.1,0.2 ?L·L-1?had a good fresh-keeping eff-ect,could not cause the 'rubber' phenomenon;after ethephon treatment,rubber-papaya so-ftening,water-soluble pectin content increased,the activity of cell wall degrading enzymes be enhanced;the low transcriptome and and expression of evm.TU.supercontig₁06.45,evm.TU.supercontig₁60.19,evm.TU.supercontig 2.231,evm.TU.supercontig₉3.34 were the main reason of'rubber' phenomenon that caused by 1-MCP.